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Chao Yu 040d2bb318 f2fs: fix to avoid deadloop if data_flush is on
As Hagbard Celine reported:

[  615.697824] INFO: task kworker/u16:5:344 blocked for more than 120 seconds.
[  615.697825]       Not tainted 5.0.15-gentoo-f2fslog #4
[  615.697826] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[  615.697827] kworker/u16:5   D    0   344      2 0x80000000
[  615.697831] Workqueue: writeback wb_workfn (flush-259:0)
[  615.697832] Call Trace:
[  615.697836]  ? __schedule+0x2c5/0x8b0
[  615.697839]  schedule+0x32/0x80
[  615.697841]  schedule_preempt_disabled+0x14/0x20
[  615.697842]  __mutex_lock.isra.8+0x2ba/0x4d0
[  615.697845]  ? log_store+0xf5/0x260
[  615.697848]  f2fs_write_data_pages+0x133/0x320
[  615.697851]  ? trace_hardirqs_on+0x2c/0xe0
[  615.697854]  do_writepages+0x41/0xd0
[  615.697857]  __filemap_fdatawrite_range+0x81/0xb0
[  615.697859]  f2fs_sync_dirty_inodes+0x1dd/0x200
[  615.697861]  f2fs_balance_fs_bg+0x2a7/0x2c0
[  615.697863]  ? up_read+0x5/0x20
[  615.697865]  ? f2fs_do_write_data_page+0x2cb/0x940
[  615.697867]  f2fs_balance_fs+0xe5/0x2c0
[  615.697869]  __write_data_page+0x1c8/0x6e0
[  615.697873]  f2fs_write_cache_pages+0x1e0/0x450
[  615.697878]  f2fs_write_data_pages+0x14b/0x320
[  615.697880]  ? trace_hardirqs_on+0x2c/0xe0
[  615.697883]  do_writepages+0x41/0xd0
[  615.697885]  __filemap_fdatawrite_range+0x81/0xb0
[  615.697887]  f2fs_sync_dirty_inodes+0x1dd/0x200
[  615.697889]  f2fs_balance_fs_bg+0x2a7/0x2c0
[  615.697891]  f2fs_write_node_pages+0x51/0x220
[  615.697894]  do_writepages+0x41/0xd0
[  615.697897]  __writeback_single_inode+0x3d/0x3d0
[  615.697899]  writeback_sb_inodes+0x1e8/0x410
[  615.697902]  __writeback_inodes_wb+0x5d/0xb0
[  615.697904]  wb_writeback+0x28f/0x340
[  615.697906]  ? cpumask_next+0x16/0x20
[  615.697908]  wb_workfn+0x33e/0x420
[  615.697911]  process_one_work+0x1a1/0x3d0
[  615.697913]  worker_thread+0x30/0x380
[  615.697915]  ? process_one_work+0x3d0/0x3d0
[  615.697916]  kthread+0x116/0x130
[  615.697918]  ? kthread_create_worker_on_cpu+0x70/0x70
[  615.697921]  ret_from_fork+0x3a/0x50

There is still deadloop in below condition:

d A
- do_writepages
 - f2fs_write_node_pages
  - f2fs_balance_fs_bg
   - f2fs_sync_dirty_inodes
    - f2fs_write_cache_pages
     - mutex_lock(&sbi->writepages)	-- lock once
     - __write_data_page
      - f2fs_balance_fs_bg
       - f2fs_sync_dirty_inodes
        - f2fs_write_data_pages
         - mutex_lock(&sbi->writepages)	-- lock again

Thread A			Thread B
- do_writepages
 - f2fs_write_node_pages
  - f2fs_balance_fs_bg
   - f2fs_sync_dirty_inodes
    - .cp_task = current
				- f2fs_sync_dirty_inodes
				 - .cp_task = current
				 - filemap_fdatawrite
				 - .cp_task = NULL
    - filemap_fdatawrite
     - f2fs_write_cache_pages
      - enter f2fs_balance_fs_bg since .cp_task is NULL
    - .cp_task = NULL

Change as below to avoid this:
- add condition to avoid holding .writepages mutex lock in path
of data flush
- introduce mutex lock sbi.flush_lock to exclude concurrent data
flush in background.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
2019-05-23 07:03:19 -07:00
arch - Fix-ups 2019-05-14 10:45:03 -07:00
block for-5.2/block-20190507 2019-05-07 18:14:36 -07:00
certs kexec, KEYS: Make use of platform keyring for signature verify 2019-02-04 17:34:07 -05:00
crypto Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-05-07 22:03:58 -07:00
Documentation - Fix-ups 2019-05-14 10:45:03 -07:00
drivers - Fix-ups 2019-05-14 10:45:03 -07:00
fs f2fs: fix to avoid deadloop if data_flush is on 2019-05-23 07:03:19 -07:00
include - Fix-ups 2019-05-14 10:45:03 -07:00
init init: free_initmem: poison freed init memory 2019-05-14 09:47:47 -07:00
ipc Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2019-05-07 22:03:58 -07:00
kernel Merge branch 'akpm' (patches from Andrew) 2019-05-14 10:10:55 -07:00
lib mm/gup: change GUP fast to use flags rather than a write 'bool' 2019-05-14 09:47:46 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm Merge branch 'akpm' (patches from Andrew) 2019-05-14 10:10:55 -07:00
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scripts gcc-plugin fix: 2019-05-13 16:01:52 -07:00
security Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-05-13 15:15:00 -07:00
sound sound updates for 5.2-rc1 2019-05-09 08:26:55 -07:00
tools pci-v5.2-changes 2019-05-14 10:30:10 -07:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt mm/mmu_notifier: convert user range->blockable to helper function 2019-05-14 09:47:49 -07:00
.clang-format Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 11:26:25 -07:00
.cocciconfig
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.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore .gitignore: add more all*.config patterns 2019-05-08 09:47:46 +09:00
.mailmap A reasonably busy cycle for docs, including: 2019-05-08 12:42:50 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Char/Misc driver patches for 5.1-rc1 2019-03-06 14:18:59 -08:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS - Core Frameworks 2019-05-14 10:39:08 -07:00
Makefile Kbuild updates for v5.2 2019-05-08 12:25:12 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.